The present invention relates to a scale for a photoelectric encoder.
Scales for photoelectric encoders are roughly classified into amplitude grating scales and phase grating scales. The amplitude grating scale has a configuration in which high-reflectance gratings and low-reflectance gratings are arranged with a certain pitch. In a photoelectric encoder, a scale is irradiated with light, and the relative position with respect to the scale is determined from the difference in the reflection of light between the high-reflectance gratings and the low-reflectance gratings.
The high-reflectance gratings are composed of a metal such as gold (Au), aluminum (Al), and chromium (Cr), whereas the low-reflectance gratings are composed of various materials or based on various structures depending on the optical principle thereof.
For background information see, for example, Japanese Unexamined Patent Application Publication No. 2000-18973 and Japanese Unexamined Patent Application Publication No. 2008-45931.